Night Terrors
by SuperWhoLockian75
Summary: After Sherlock returns from his 3yr escapade taking down Moriarty's web, John begins to notice him having bad dreams. But these "nightmares" aren't what they seem; something dark has escaped from Sherlock's Mind Palace and now it's wreaking havoc on Sherlock's memories. Can John help Sherlock stop it in time? Or will he lose Sherlock to the memory that should've stayed hidden?
1. Power Outtage

Most nights were pretty good since Sherlock came home after those 3 long years of fighting, running, and being oh so clever. It was definitely quite a shocker when he showed up at the flat for the first time while John was making tea in the kitchen. It cost John a pretty nice tea pot that Mrs. Hudson had given him as a birthday present as consequence. Getting back into the rhythm of things again did take some effort and, after an equally shocking visit to Lestrade, they were back solving mystery after mystery as if nothing had happened.

But there were some things that Sherlock didn't like to talk about; things that John knew haunted his mind every now and then because he could recognize it on Sherlock's face as he did years ago on his own after getting back from the war. He wouldn't say it was PTSD, Sherlock was too resolved and clever for those illusions and flashbacks to fool him, so John summed it up to simply bad memories. Until those bad memories started to come to life, so to speak.

It was a particularly cold evening in March in the flat on Baker Street mainly because the heating had quit after a power outage occurred several hours prior. John and Sherlock made use of the fireplace in the sitting room and a makeshift campsite was now present in front of it. The fire was nice and toasty, but it didn't reach past the sitting room by any means which included their respective bedrooms, forcing them to take refuge in front of the fire hopefully for just the one night. Of course no power meant no internet or TV which didn't leave much for Sherlock to focus on other than the forever changing flames within the fireplace, and even that didn't occupy him for long.

"Bored." Sherlock mumbled. He was sitting in front of the fireplace with his long legs tucked under his chin and his equally long arms wrapped around his legs. His chin was resting on top of his knees while his eyes were focused on the flames. John, on the other hand, was dozing in his armchair comfortably covered in blankets with a cooling mug of tea on the table next to him. He lifted his head slightly with half-opened eyes and frowned at Sherlock.

"Well, it is after all night time, did you ever think about, I dunno, _sleeping_?" John asked with a hint of sarcasm and an obvious tiredness to his voice. Sherlock just tugged the quilted blanket around him closer and said nothing. John sighed and snuggled in further into the chair.

"Well you're not gonna start shooting the wall again at two in the morning, so go to your mind palace or something and—_yawn_—chase some old bad guys around…" John murmured towards the end and was soon drifting back off to sleep. Sherlock looked up at his friend from the floor and made a noise of exasperation with a hint of jealousy.

"I wish I could…" Sherlock whispered to himself. Reluctantly, he stood up with the blanket still wrapped around him and pushed his leather chair closer to the fireplace where it would definitely retain the heat the fire was putting out. Animal skin had a lovely way of doing so. After becoming content with the surface temperature of his chair, Sherlock settled down in it and pulled his legs up to his chest; minimizing the amount of space where his body heat would escape and rewrapped the blanket around him for better coverage. With a heavy sigh, Sherlock settled in and placed his head on the back of the chair; staring up at the ceiling almost willing it to start cracking or to do something interesting. But of course it didn't so Sherlock closed his eyes and did as John suggested, he searched his Mind Palace for something interesting to remember.


	2. The Mind Palace

Most people using this technique had simply a road or a room or two to help them remember things easier, but Sherlock wasn't like most people. In every sense of the word his Mind Palace was every meaning of the word "palace" with its several stories and countless rooms, its ornate decorations and furniture, and its vivid images placed all around the giant structure. Each step brought him back further and further to memories and events from long ago that anyone else would forget after a few minutes of experiencing. But to most people ordinary things that occur in their everyday lives aren't that important in the first place to bother remembering. Except for Sherlock, where these things made his job possible.

He entered through the tall and decorated front gate and began walking down the long drive to the palace. Already memories from decades ago were coming into focus, but these things weren't what he wanted to remember right now. With practiced effort, Sherlock focused on the top floor and northern wing of the building and soon found himself time-jumping there. It was a little different than teleporting because there was no disappearing and reappearing somewhere else, it was as if he took one long step and everything around him stretched and warped until he was where he wanted to be. Now he was placed in the middle of a finely carpeted hallway where golden candelabras illuminated the walls as well as a chandelier atop a four-way intersection further down the hall. The walls were wallpapered the familiar pattern of the sitting room in 221B and Sherlock found himself placing a hand on it, finding comfort in the place he now called home with the only person he'd ever consider sharing it with. These hallways were specifically reserved for his memories with John at the flat hence why they were so finely preserved and cared for, but there was something odd further down the hall that wasn't supposed to be there.

Sherlock walked down the seemingly endless hallway, passing dozens of rooms where memories of him and John were always being replayed and catalogued for relevance. If one of them seemed to have outlived its usefulness, it was discarded and renovated for a new memory to take its place. However, this rarely happened in this section of the northern wing lately, considering how long Sherlock had been away from John he wanted to make sure he held on to whatever memories he could of them. Those memories were what kept him alive every now and then during those three years.

As he was approaching the seemingly damaged part of the hallway, Sherlock felt something different change. There was no clear distinction as to what, but _something_ had definitely been altered, and not by his own doing. The air in the hall felt as if it was slowly getting sucked out and Sherlock began finding it hard to breathe. This wasn't supposed to be happening, not here. Not in his Mind Palace. This was where he could go and shape everything into the image he wanted and needed to see, where he could remember all the good times and learn from the bad times. And now it looked as though the palace had a mind of its own.

Now at the section, Sherlock could see what was wrong but couldn't believe his mind's eye. Wall after wall and door after door was scorched nearly black and what was left of the wallpaper was peeling away and was distorted. The candelabras hung off of the walls at odd angles and were badly damaged from the apparent flames while some of them were just plain gone. The fine rug that once held a complex and beautiful pattern was now torn and ashen, parts of the wooden floor showing underneath where the rug no longer covered. Even the sturdy wooden doors made from maple wood much like most of his violin were beginning to crumble and blacken. Sherlock braced his back against an opposite wall and sank to the floor, staring in horror at what had happened. It was possible that a memory had gone rogue, so to speak, but there was no event in his life that directly linked to a fire. Sure there were the odd experimental explosions here and there and that one time in Baskervilles with the mind field, but nothing like this. This could be compared to a standard house fire or worse, arson, and nothing like that had ever happened to him before.

Sherlock brought his legs up in front of him and placed his elbows on top of his knees, bowing his head and placing his hands on the back of his neck trying to think. What memory could possibly have done this? It was going to take several hours of deep thought just to fix this section of the hall, and God only knows if any other part of the palace was damaged. After all, the actual size of the palace was always growing because Sherlock was always remembering; always cataloguing what was and what wasn't important. Lifting his head up and leaning back against the wall, Sherlock knew he'd have to go in the one wing he thought he'd never have to go in again.

The Dungeon Wing.


	3. What's Buried Should Stay Buried

Back in reality, the fire in the fireplace was beginning to simmer back down to embers and the resting bodies of John and Sherlock could feel it. The sudden chill woke John and his sleepy eyes focused on the dimming flames, then he sighed knowing he'd have to get up and get cold in order to freshen up the fire. Making sure to keep his jacket and a blanket close around him, John rose from his chair and walked over to the fireplace to add more wood to it when he glanced over at Sherlock's seemingly sleeping figure. There was something seriously wrong. The extinguishing fire now forgotten, John dashed over to Sherlock and saw that he was sweating despite the cold and the fact that he only had one blanket on to counteract it. His eyes were dashing about below his eyelids which could be easily mistaken for REM sleep, except for the fact that his arms, hands, and such were still moving slightly. John knew that the body was paralyzed during REM sleep, therefore making that solution impossible. For a fleeting moment he relaxed slightly, thinking it could just be a nightmare, until a hand shot out and grabbed him around his throat like a vise. Out of instinct, John grabbed at Sherlock's hand with both of his own and tried to pull it loose, but the fingers wouldn't budge.

"Sherlock—" John choked out even though he knew his efforts were futile. Surprisingly Sherlock's eyes shot open and stared emptily back at John's; completely void of consciousness and emotion. His face, however, shone of rage and hatred for the person he was trying to choke the life out of in his dream. John fought to catch his breath and free the grip that was slowly crushing his windpipe, but the world around him was gradually becoming blurry and hard to focus on. "Sherlock stop!" He croaked out again in a last-ditch effort to awaken his friend, but Sherlock's eyes were still unseeing and John was quickly running out of air.

* * *

Sherlock had managed to make his way out of the cindered hallway, down the cobblestone staircase, and finally into the Dungeon. It was much safer for him and his memories if he traveled on foot rather than a time-jump because the Dungeon was full of memories that were corrupt and dangerous, but still necessary to remember. If he time-jumped in the wrong spot down here the chaotic images and feelings would most certainly overtake him and keep him trapped here for an unknown amount of time. It was impossibly dark and cold, but vibrated with an uneasy energy that Sherlock had all but forgotten about. A few torches lined the cracked walls at inconsistent intervals causing odd periods of lightness and darkness as he walked down the corridor.

The doors down here were far different than the ones in the palace; for starters, they weren't made from wood but instead reinforced steel and had a small rectangular shaped peep-hole built into it with a matching hinged cover. This was so Sherlock, if he so wished, could look inside for only a moment to gather the info he needed then close the window and move on. Each door was numbered starting at 1 and ended at God only knows where for there were always going to be bad memories Sherlock would need to hold onto for information. As he passed door number 20 nothing seemed to be out of place, until he stopped in front of 21.

"Oh no…" Sherlock spoke quietly as he saw the wreckage that used to be the cell that contained a memory from a murder he never wanted to commit. The steel door was nearly off of its hinges and was hanging oddly outside the cell. It was incredibly dented and the number "21" that was plated on the front of it was starting to fall off. On the inside it was almost completely dark except for the one hanging light on the ceiling that shown a dull yellow, casting the rest of the room in shadow. If this memory was loose inside his Mind Palace, it could easily wreak havoc on his retained memories and destroy them. If that happened Sherlock would lose everything; his memories of his childhood, who Lestrade and Mycroft were, and even John and how important he was to him. Sherlock couldn't let that happen.

Gathering all the courage and strength he had, Sherlock slowly stepped into the cell; carefully using his peripheral vision to gauge any unseen threat in the shadows. Once underneath the yellow glow of the ceiling bulb he did a 360 trying to peer into the darkness for any clue as to how this memory could've gotten loose. There wasn't anything abruptly obvious that he could see—until a hand launched out from the shadows and clamped itself around Sherlock's throat, pinning him to one of the metal walls. Sherlock immediately grabbed onto the assailants wrist with both of his hands trying to pry its grip free of his throat, but the effort only made the figure squeeze tighter. He could feel his pulse pounding in his head and the crushing pressure against his trachea as the memory clamped tighter and laughed a deep, disturbing laugh that Sherlock could've sworn he'd destroyed months ago. As his vision started to swirl and waver, he knew that if he died here he would perish in real life too; that was how the body worked and, if it was starved of the mind, then everything else would die.

Sherlock would have none of that.

With his last remaining strength, he brought up his knee abruptly and slammed it into the assailant's groin causing him to release Sherlock's throat and stumble back clutching the injured area. Sherlock doubled over, coughing and gasping for breath and rubbing his now-bruised neck with his hand. He looked up at the shadowed figure, whom of which seemed to recover faster than Sherlock expected, and straightened himself.

"I should have known better than to just leave you in this standard cell, you're much too volatile for it aren't you?" Sherlock scolded himself with a raspy voice and coughed lightly, then continued. "I suppose some things are better left forgotten than remembered, I'll keep that in mind next time."

"There won't be a next time." The voice from the memory spoke with a clear English accent and harshness to it. He then stood right below the hanging light where Sherlock would be able to see him more clearly.

"We'll see about that, Sebastian. This time you don't get a cell, but instead the incinerators where you won't harm anything ever again… at least not in here." Sherlock retorted and took a couple steps towards him, but Sebastian held a hand up.

"Do you really think it's going to be that easy? I'm out now, and it's time to have a little _fun_; especially after what you did to the boss." He sneered at the last part, knowing full well what became of Moriarty.

"_I_ did nothing; _he_ was the one who shot himself in the head much to my own surprise. So don't blame me for your boss's stupidity." Sherlock snapped, but Sebastian just shook his head and smiled.

"_You_ were the one who beat him, and he couldn't take it, therefore his unfortunate end occurred. As far as I'm concerned that means you're the one responsible, Sherlock Holmes, and now I'm going to take it out of your hide… or rather the interesting part of the inside of it." Sebastian stated while splaying his arms and doing a slow 360, gesturing that he meant the destruction of the Mind Palace.

"I'd like to see you try, you're just a memory that can be easily deleted; like so." Sherlock snapped his fingers, expecting Sebastian to disappear, but much to the detective's surprise he remained exactly where he was. The ex-army man slow-clapped and laughed at the look on Sherlock's face.

"Oh wow, I can't believe you actually thought that would work! Moriarty _was_ right about one thing—your ego." Sebastian took a few steps towards Sherlock until they were at least two inches away from each other's faces. "It's gonna take more than just a snap of your fingers to get rid of me clever boy; it's harder to clean up something filthy rather than polish something that's clean." He smirked and chuckled, clearly amused with himself and Sherlock's current predicament. Without a moment's hesitation, Sherlock launched a right hook into Seb's cheekbone, abruptly sending him on his ass and most likely breaking the bone.

"God I hate it when people like you think they can be smartasses." Sherlock sneered and shoved Sebastian on his back with his foot, then placed it like a lead weight on his trachea. "Now then, before I end your existence, for good this time, do you have any last words?" Sherlock asked with a tone that suggested he was quite bored of the situation. Sebastian spit out a mouthful of blood and clutched at the ankle that was currently attached to the foot that was crushing his windpipe.

"Only that I'll enjoy crushing the life from your blogger before you do." Sebastian choked out and grinned.

"What did you just say?" Sherlock demanded through gritted teeth and pushed down harder with his foot.

"You… may have free reign in here… but your body… is now my _play toy_." Sebastian laughed and Sherlock immediately withdrew his foot, realizing the seriousness of the situation.

"What've you made me do?!" Sherlock demanded in complete rage. If he had done anything to John because of this… _oh God no_… Sebastian merely laughed and sat up, wiping the blood off his face.

"Something you'll regret when, or _if_ you ever wake up." Sebastian sneered and within the blink of an eye vanished from the cell.


	4. For John

**Terribly sorry this is so short, but this story will be wrapping up relatively soon. Had to find a place to break it when I was typing it up in Word. Enjoy!**

"_No!_" Sherlock screamed and lunged for the apparition, but it was too quick and all he managed to grab was air. He slammed his fist down angrily on the concrete floor. "I swear to God if you've hurt John…" He muttered to himself and shut his eyes, attempting to control his anger. _No, emotions will only inhibit you. Focus on the facts. Focus on John._ He quickly imagined himself inside the living room of 221B and when he opened his eyes it was almost like an out-of-body experience. He was standing a few feet away from his transport—that of which was currently trying to choke the life from his friend.

Sherlock immediately reacted and tried grabbing at his transport to pull him off, but it was to no avail; his hands went right through his transport's wrists. Sebastian was in control of his body now. _Think dammit!_ Sherlock scolded himself, clenching and unclenching his fists in frustration. John's complexion was turning bluer by the second and there was nothing he could do. _Unless…_

Without a better option, Sherlock lunged forward and jumped into his body, which was safe to say incredibly odd since he knew he was already in his body and… well, he didn't want to go into great detail about it. Sherlock could feel John's throat as it was being crushed beneath his hands as well as Sebastian's memory fighting for control over the transport in his head. There was only one option; complete shutdown. It was the only way to restore Sebastian to where he truly belonged and to regain control over his transport.

It was also the only way to save John.

Sherlock focused on his memories of John and could feel them give him strength. _This would work_, he told himself, _it has to_. Somewhere off in the distance he could hear Sebastian screaming, either in agony or for him to stop Sherlock couldn't tell which. He just had to last a little bit longer… he could feel his grip lessening on John's throat and heard John as he took a slight breath._ Not enough._ Sherlock told himself and forced Sebastian to relinquish control of the transport, but the memory was stronger than he anticipated.

"Sherlock!" John choked out. "Fight it! You have to—_ack!_—fight it!" He pleaded, and that was all Sherlock needed to turn the tables.

The sudden memory of him and John clasping hands, handcuffed, and running came into full view. It was one of his fondest memories of John, and the one that would send Sebastian back to the hole he busted out of.

Sherlock screamed and everything went black.


End file.
